1. Field of the Invention
The present invention relates to the fields of liquid spray and atomization of liquids of all kinds and, more specifically, finds utility in humidification and misting, industrial cleaning, surface coating and treatment, particle coating and encapsulating, fuel atomization, deodorization, disbursement of insecticides, aerosols, and medical spray applications.
2. Description of Related Art
Many types of ultrasonic fluid ejection devices have been developed for atomizing of water or liquid fuel. These atomizers can be classified into two groups. The first type atomizes liquid that forms a thin layer on an ultrasonically-excited plate. The first type is not capable of ejecting atomized fluid droplets. U.S. Pat. No. 3,738,574 describes an atomizer of this type.
The second type utilizes a housing defining an enclosed chamber. The housing includes a perforated membrane or a pinhole membrane as the front wall of the chamber. The apparatus further includes a means to vibrate the membrane or a side wall of the chamber, typically by a piezoelectric element affixed to the front face of the chamber. The piezoelectric element oscillates the fluid in the chamber. As a result, pressure waves are generated in the chamber, forcing fluid through the open pinholes. All the devices of the second type require fluid to be kept inside the chamber next to the discharge opening. When volatile fluids are used, problems arise. The volatile fluids escape through the discharge opening. Hence, liquid may undesirably outflow from the opening. The discharge opening will clog, restricting or stopping further discharge. These problems are prevalent with volatile fluids such as fuel, paint, or other coating materials. To overcome at least some of these problems, U.S. Pat. No. 4,533,082 uses a vacuum pump to ensure that the liquid in the chamber is kept under negative pressure to prevent outflow.
Other variations of apparatus for ejecting atomized liquid, utilizing one of the above two types, are disclosed in U.S. Pat. Nos. 3,812,854, 4,159,803, 4,300,546, 4,334,531, 4,465,234, 4,632,311, 4,338,576, and 4,850,534.
Certain writing instruments, such as fountain pens, employ mechanisms for controlling the flow of ink from a supply container to the writing tip of the pen.
The present invention provides an ejection device that includes a free oscillating surface having microscopic tapered apertures of a selected conical cross-sectional shape. A layer of fluid adheres in surface tension contact with the oscillating surface. The apertures draw fluid into their large openings and eject the fluid from their small openings to a great distance. The ejection action is developed by the aperture, regardless of the amount of fluid in contact with the oscillating surface, and without any fluid pressure. Both sides of the oscillating surface are operating under the same ambient pressure. Therefore, the ejection device can operate equally well in vacuum or high-pressure environments. The supplied liquid continuously adheres to the large opening by surface tension. The film of fluid oscillates with the surface while it is being drawn into the large opening of the aperture and ejected forwardly. This continues until all the fluid is drawn from the surface, leaving the surface dry and free of liquid during the time that the device is not in use.
If the cross-section of the aperture is chosen with respect to the fluid to be ejected, the oscillation required to produce ejection is kept small, and the film of fluid on the oscillating surface appears to be dynamically at rest during ejection. By supplying only enough fluid to continuously form a thin film, in surface tension contact with the oscillating surface, to the side containing the large openings of the tapered apertures, neither clogging nor uncontrolled emission or leakage through the apertures occurs. The device can operate under any pressure conditions.
In an alternative embodiment, the invention provides an apparatus for dispensing liquids as an atomized spray. The apparatus preferably includes a vibratable member having a front surface, a rear surface, and at least one tapered hole extending therebetween. The tapered hole has a larger cross-sectional area at the rear surface than at the front surface. A means is provided for vibrating the member, and a supply container is provided for holding the liquid to be dispensed. A means is provided for delivering the liquid from the supply container and to the rear surface of the vibratable member. A flow regulator is further included for regulating the flow of the liquid from the container and to the vibratable member. The flow regulator is configured to allow delivery of the liquid to the rear surface in volumes that are substantially equal to the volumes dispensed from the vibratable member. Preferably, the liquid is delivered to the rear surface of the vibratable member at a rate that is substantially equal to the rate of the liquid being dispensed from the front surface. In this way, the flow of liquid from the supply container and to the rear surface is regulated so that neither insufficient nor excessive amounts of liquid are delivered to the rear surface. In this manner, an optimal amount of liquid is provided to the rear surface during operation of the apparatus.
In a preferable aspect, the flow regulator includes an air vent that is in fluid communication with the supply container. When open, the air vent allows air to flow into the supply container in volumes that are sufficient to replace the volumes that are delivered to the rear surface. In this way, delivery of liquid to the rear surface can be controlled by regulating the amount of air flowing to the supply container. Preferably, opening and closing of the air vent is controlled by the liquid itself as it travels from the supply container and to the rear surface. As liquid flows from the supply container, some of the liquid flows into and closes the air vent thereby preventing air from entering the supply container. As liquid continues to flow from the container, a vacuum is created in the container to prevent additional flow of liquid from the container. Upon ejection of liquid from the vibratable member, liquid in the air vent flows to the rear surface to replace the ejected liquid. In this way, the air vent is again opened to allow air to enter the container and to allow additional liquid to flow from the supply container.
In a further aspect, the supply container is preferably oriented in a position that facilitates the flow of liquid from the container and to the rear surface. In another aspect, the air vent is distanced from the supply container at a distance sufficient to allow the liquid to be delivered to the rear surface at a rate that is substantially equal to the rate of liquid dispensed from the hole.
The invention further provides a method for dispensing liquid droplets as an atomized spray, with the liquid being delivered from a supply container. According to the method, liquid is delivered from the supply container and to the rear surface of a vibratable member in an amount sufficient to cover a hole in the member with liquid. The liquid is held in the hole by surface tension. The vibratable member is then vibrated to dispense at least a portion of the liquid through the hole, with the liquid being dispensed from a front surface of the member. Additional liquid is delivered from the supply container and to the rear surface in volumes that are held in surface tension contact to the rear surface of the vibratable member, i.e. the entire volume of liquid that is delivered to the rear surface is held to the rear surface by surface tension forces so that the delivered liquid will remain attached to the rear surface until ejected. Preferably, the liquid is delivered to the rear surface at a rate that is substantially equal to the rate of the liquid being dispensed from the front surface.
In an exemplary aspect, preselected volumes of air are exchanged with liquid from the supply container to deliver the additional volumes of liquid to the rear surface. Preferably, the preselected volumes of air are sufficient to replace the volumes of liquid that are delivered from the supply container and to the rear surface. In this way, by controlling the supply of air volumes to the supply container, the amount of liquid delivered to the rear surface can be regulated. Preferably, the supply of air to the supply container is controlled by opening and closing an air vent that is in communication with the supply container. In one aspect, the air vent is closed upon filling of the air vent with liquid from the supply container as the liquid flows toward the rear surface of the vibratable member. As liquid is ejected from the vibratable member, liquid flows from the air vent and to the rear surface to replace the ejected liquid, thereby opening the air vent and allowing air to flow into the supply container. In turn, the air supplied to the container allows additional liquid to flow from the supply container and the process is repeated until vibration of the member is ceased.
The rate of liquid dispensed from the vibratable member can widely vary depending on the number of apertures and the size of each aperture. In one particular aspect which is not meant to be limiting, the liquid is an insecticide which is dispensed at a rate in the range of approximately 0.1 cm3 to 10 cm3 per hour, and more preferably at about 0.5 cm3 to 2 cm3 per hour. Preferably, the insecticide is ejected from the front surface in droplets having a mean size in the range from 1 xcexcm to 15 xcexcm, and more preferably at about 3 xcexcm to 10 xcexcm. In another aspect which is not meant to be limiting, the liquid is a deodorant, usually an air freshener, which is dispensed at a rate of approximately 0.1 cm3 to 10 cm3 per hour, and more preferably at about 1 cm3 to 2 cm3 per hour. Preferably, the deodorant is ejected from the front surface in droplets having a size in the range from 1 xcexcm to 15 xcexcm, and more preferably at about 3 xcexcm to 10 xcexcm.
In another embodiment of the invention, an apparatus which is particularly useful as an insecticizer or a deodorizer is provided. The apparatus includes a housing having at least one ejection port and a vibratable member within the housing. The vibratable member includes a tapered hole that is aligned with the ejection port. A means is provided for supplying liquid to a rear surface of the vibratable member, and a means is provided in the housing for vibrating the member. The housing is conveniently configured to receive a liquid supply container for holding a deodorant or an insecticide. When connected to the supply container, the apparatus can be placed at a strategic location and actuated to dispense the liquid. In a preferable aspect, a battery is employed as a power source to vibrate the member, thereby allowing the apparatus to be placed in a variety of locations and to be left unattended while dispensing liquid.
In another exemplary aspect, the apparatus is provided with a controller for controlling actuation of the vibratable member. Preferably, the controller is preprogrammed to cyclically actuate the vibratable member according to a preselected ejection schedule. Such a configuration is particularly useful when dispensing an insecticide which requires careful control of the amount of insecticide that is dispensed into the atmosphere. In another preferable aspect, upon depletion of the liquid from the supply container, a refill supply container can be attached to the housing and the apparatus reused. In still a further aspect, the refill container is provided with a pair of N size cell batteries which serve as the power source to vibrate the member. The batteries are provided with sufficient energy to eject the full content of the refill.